Feature/refactor slider

- Improved controls (First/Previous on LHS and Next/Last on RHS above the displayed card)
Also, if you aren't already aware, you can scroll through the Card Slider using horizontal mousewheel/touchpad.
- Moved the functionality of controls to lib.js (where slider class is defined)

- Card location displayed in between the buttons with a display similar to that in Kindle
- jQuery horizontal slider above the controls to select cards anywhere in the deck
- Modified the Slider class so that the current card is always centered in the Card Slider (except for the first and last two cards of course)
- Re-sizing the window no longer moves the slider position to 0
- The front side of the each card is displayed in the card slider
-  the slider is displayed only after it has been correctly loaded. Looks much better than the previous version where all the card thumbnails were displayed at first and then reconfigured.